The aim of this project is to study the synthesis, mechanistic aspects, and the biological activity of a series of platinum complexes containing the platinum dichloro moiety complexed to known active antitumor agents. The present work has concentrated on the mechanism phase, spcifically of determining the sites of distribution of these agents, in order to predict the nature of a possible biological effect and thereby identify a rational mode of administration of such an agent to test animals in order to elicit maximal biological activity. A primary procedure to achieve this objective had been attempts to label cis-dichlorodiammine platinum with tritium in order to determine the distribution of such a radiolabeled complex. Present work with 195mPt has indicated that that radionuclide, because of its high yield of Auger and conversion electrons, is capable of providing this same information. This part is in itself, we believe, a major step forward in trying to assess mechanisms of action of platinum compounds. The ability to use Auger and conversion electrons for subcellular autoradiography is a procedure that had not been clearly understood and has not been exploited heretofore and may prove useful in a number of other compounds of biological interest. Finally, the relative stability of these complexes is being studied by an analysis of the kinetics of exchange of both the carrier and the leaving ligands, using specially prepared short-lived radionuclides, such as 38Cl and other chlorine radionuclides.